Constant pressure, constant flow control valve



March 19, 1957 F. JAsEPl-l CONSTANT PRESSURE, CONSTANT RLOw CONTROL VALVE Filed Aug. 7. 1955 S RO S United States Patenti t i CONSTANT PRESSURE, CONSTANT FLOW CONTROL VALVE Lawrence F. Jaseph, Memphis, Tenn., assignor to Dover Corporation, a corporation of Delaware Application August 7, 1953, Serial No. 372396 13 Claims. (Cl. 121-46.4)

jack to the reservoir, and an electric control circuit. Such pumping and controlling unit is disclosed in Lawrence F. Jaseph Patent No. 2,355,164, dated August S, 1944, and entitled Elevator Control. ln such installations the elevator is lowered by opening the lowering valve to a predetermined degree, but since the elevator moves downwardly under the force of gravity, there is` no provision to hold the speed at the same and a constant rate during the lowering of dierent weight loads. Furthermore, if accidental rupture of the tluid line between the jack and the lowering valve occurs, the elevator will descend out of control and at a speed substantially, and perhaps dangerously, in excess of the normal speed.

The control valve of the present invention is eiective to overcome both of these difficulties. It will minimize the speed variations during lowering regardless of' thel loading on the elevator. With a pipe line rupture during either raising or lowering of the elevator opening a substantially larger passage than olered by the lowering valve, during a normal lowering movement, to permit downward overspeed of the elevator, complete shutoff of uid ow from the jack will be obtained to bring the elevator to a halt. When fully shut olf by overspeed in this manner, the control valve may be automatically reset for normal operation of the apparatus by the restoration of operating pressure to raise the elevator.

ln orderto obtain the maximum benefit from the control valve of the present invention, it is preferred that it be installed at the juncture of the uid line with the jack, and it actually forms a convenient connection between the uid line and the jack.

It is a principal object of the present invention to provide a new and improved control valve for hydraulically operated elevators, which will regulate the descending speed of the elevator regardless of the load, thereby providing a substantially constant speed, the rate of which is determined by the setting of the lowering valve.`

lt is another object to provide a new and limproved control valve for hydraulicallyv operated elevators, which stops the elevator descent when its speed becomes Vexcessive due to any of a number of factors, including pressure failure in the line between the jack and the. lowering valve.

Another object is to provide a new and improved con trol valve which will bring the elevator to a halt upon rupture of the uid supply line. y

Another object is to provide a new and improved con- 2,785,660 VPatented Mar. 19, 1957 ice trol valve having the foregoing characteristics, which can be restored to service merely by.restoring the normal operating pressure in the uid ow line.

A further object is to provide a new and improved control valve having the foregoing characteristics, which can be restored to service merely by operating the elevator in the ascending direction to bring the fluid supply line to uid operating pressure.

Still another object is to provide a novel control valve for hydraulically operated elevators, which is fully automatic in its operations of maintaining constant the speed of the elevator in the descending direction, and bringing the elevator to a halt when that speed becomes excessive due to pressure failure.

A further object is to provide a new and improved control valve which, with slight modifications, can be used only as a speedcontrol or regulating device, or as a safety device.

A further object is to provide a new and improved speed control and safety valve for hydraulically operated elevators, which may be used with presently available pumping and controlling units.

Other objects and advantages will become apparent from the following description taken in conjunction with the accompanying drawings, wherein:

Fig. l is a diagrammatic view of the hydraulic portion of a controlling and pumping unit, showing the control valve of the present invention installed at the junction between the uid line and the jack; and

Fig. 2 is a cross-sectional view, on a greatly enlarged scale, taken substantially along the line 242 of Fig. l, showing the control valve in medial crosssection with the valve components in the position which they would normally occupy when lowering an empty elevator car at maximum speed setting of the lowering valve.

The control valve of the present invention, indicated generally by the reference character 10, is mounted on the cylinder 12 of a jack14 having a piston 16 reciprocablein the cylinder, and carrying at its upper end an elevator car or Vcage 18 of conventional construction. The control valve 10 has a port 2d which is connected to a fluid line V2.2 leading from a combinedV lowering and direction controlling valve 24, one port of which is connected by a conduit 26 directly to the reservoir or tank 28 and the other port of which is connected by conduit 30 to the outlet from a motor driven pump 32 which receives uid from the reservoir 28 through a conduit 34. Either the outlet from the pump 32 or the valve 24 is provided with a check valve v(not shown) to prevent reverse ow of hydraulic liquid through the conduit 30 and pump 32. l

When it is desired to raise the elevator, fluid is pumpedY from the tank 28 by the pump 32 through the conduit 30, valve 24, conduit 22, valve 10, and into the cylinder 12. WhenY it isV desired to lower the elevator 18, the lowering valve 24 is set for a particular descending speed rate and huid is expelled by the weight of the elevator cage ,18, its load and'piston 16 from the cylinder 12 through the control valve 10, conduit 22, valve 24, and conduit 26 to the tank 28. The descent of the elevator should be at a rate of speed determined by the setting of the lowering valve, but -it has been found that the speed will vary substantially in accordance with the weight or load of the elevator car 18, its contents, and the plunger 16 unless governed by the control valve 10, which will maintain the descending speed substantially constant and at the ratel dictated by'the setting of the lowering valve 24, regardless of whether the elevator 18 is empty or isloaded to capacity.

While the control valve is of the reversible llow type,

that is, uid may ow through it in'ether of two direccontrol system.

YA2,'rezbeeo tions, it functions automatically as a control or safety valve only when the fluid ows through 1t from the )ack 14'toward theV reservoir 28 or the pump 32. This ow Y direction obtains when the lowering valve 24 is open or when there isa rupture in the line communicating the jack with the reservoir or pump. In the latter case there is a sudden loss of line pressurerwhich allows the elevator cage to descend,rand obviously the rupture may occur atfany time during the operation of the elevator Y In View of this, the following description will consider the normal operating condition of the valve to exist when the elevator cage-1S is descending and the hydraulic uid is owing from the jack cylinder 12 either under a normal descent or under an emergency descent caused by a failure in the hydraulic System downstream from the jack. Y j Y 4 The control valve 10 has a main valve'body 36 provided at one end with a ange 38 secured by cap screws or bolts 4t) to an Yadapter 42 welded to the wall ofthe cyl- Y inder 12, and encompassing an opening 44 therein. The control valve 10 is thus mounted directly on the jack cylinder` 12 so that its maximum safety features can'be The piston 72 is formed opposite the guide 70 with an integral stem portion 92 and piston 94 of smaller diameter than the piston 72, thelatter being reciprocable in a cylinder 96 formed in the'cap 78. The piston 94 is sealed against the cylinder 96 by a resilient cup shaped sealing member 98 held in place by a Washer 100 and a split retaining ring 102 seated in an annular grooveV 104 inthe outer end of the piston stem 912. Y,

The piston 72 is biased in the valve opening direction by a relatively strong orV heavy springj106 having a low rate, so that its force will vary Vas littley as possible over the travel of the piston 72, and which. is conned beV tween a pair of spring'keepers 108 and 110 within a Vcylindricalthousing 112 having its inner end Welded toV the piston 72 and stern 92 is closed by a plug 116, gasket.

utilized, and any failure of the system between the con- Y trol valve't') and the lowering Valve 24 will cause the control valve 1G to bring the elevatorlV to a halt.

The valve body 36 is formed with a main cavity or chamber 46 communicating freely with the port 20 and bounded by a wall 48 at the end'of the body 36 adjacent the cylinder 12. The chamber 46 communicates with the cylinder 12 through a smoothly bored orifice,

Yopening or aperture V58 Vin the wall 48, and in which a valve member 52 is reciprocably mounted. The'valve Y member 52 is provided or formed with an enlarged head `54' on the cylinder or: upstream side'of'the'aperture 50 to prevent uits passing completely therethrough .toward the chamber 46,' andV which when the valve is closed,

depth. .The narrow slots 69 reduce the capacity ofthe opening 50 to about 40% `of its completely unobstructed Y`size and also reducertheturbulence of hydraulic'uid under pressure lowing in either direction through the opening. l The. valve member 52-is provided with a plurality of guide wings 62, preferably three, which center*V the valve in the opening when'itV is moved to its fullyY 118, and splitV retaining ring seated in an annularV groove 122 in the bore 82. The keeper 110 bears against the inner end of a bolt 124 extending through a tapped cap 126 closing the outer end of the housing and by means of which the pressure exerted Vby the spring 106 can be adjusted. A lock nut 128 maintains the bolt 124 in its adjusted position, which should be that at which the force exerted by the spring will not quite move piston 72 against the hydraulic pressure produced by the Weight ofan empty elevator car 18;

The space inthe cylinder 74 between the piston 72` and the piston 94 and `the cap 78V communicates with the interior of the jack cylinder 12 through a passageway,

130, pilotpor safety valve 132, and a passagewayf134, the passageways 138 and 134 being bored or cored inlV the valve Vbody 36. So long as the valve 132 establishes communication, between `the passageways 130- andV 134,

jack cylinder 'Yuid pressure exists in the cylinder 74,' The area of thepiston 72 is very nearly equalV to the sum of the areas ofthe piston 94 andthe effectiveV area of the valve seatY 56,;so that Vthepressure on thehead54 of the valve member 52vis completely balanced by equal pressure on the exposed equal differential piston areasY in the cy1inder'74. t The head ofthe piston 94 is exposed to atmosphericrpressure through the'open Vend .of the `cylin'derf96 and a port 136 'in the housing v112. Thus Y Y f when the valve 132 permits communication between theV Y jack cylinder 12 and valve cylinder 74, jack pressure has Y no inuenceon the position of the valve member 52. Y

open position by the reverse ow of uid from the' cavity j. 46 to the cylinder 12 during the upward movement of the elevator.

' The valve member 52 is formed with an integral axial shank 674 and stem 66 of reduced diameter to provide ashoulder 68 between thestem 66 and shank 64. The

stem 66' is sliclable in' a bore'69 in a Aguiding portionV 70 of a piston 72 reciprocablein' a cylinder 74 formed` in the cuide' body 36 and Vcoaxial with the opening 50.

The-stem166 projects, into an Venlarged axial counter bore 82fin vthe piston 72, Yand is fitted at its'oute'r endV with ascup 84V held thereon by a'splitringSG in; a lstern.VV Vg'roove, with the openend VVofj the cup facing' .inwardlyv Y ofthe stem; A'light spring '98 confined between-the sure Vin the main valve cavity 46 Aacts to move the Vpistons 72 and 94 in the direction of valve'V closing overan area cylinderf12gand the light'spring'9V to'closethe valve 52. Y

The. piloter safetyfv'alve 132 Vis housed in aV valve base of the cup 84 and the linnerfed of the bon-:82 in Y Y wardrthe piston 72 so that the shoulderr68 no'rrnallyV abuts the Vouter endk 8470i the guidejportion 70.' "The cupV 84 g limits the .movement of'thestem766 'outwardly of theV piston, that-Vis, inthe direction. of the: valve lopenin'gor tojrthe leftY as seen in Fig. 2. "Dashpot action yof the stern 66 in the axial bores 69-and 82V is preventedby transverse' passages 87 inthe guideV 70r connecting Ythe Vvbore 82and chamber46.; Y

`the Vpiston 72 urges the ,stem and' valve member 52Yto- The pressure in the pipe line 22 and main valve cavity 46 acts on the valvemembei' 52 in valve opening direc-y tion Yand on the piston 72,` tending to move it in such direction as to permitrthe valve 52 to close, but since' the difference in the effective areas of the valve member` 52V`and the piston 72 is exactly equa-l "to the eiective area of the piston94, the neteffect is that rtheline presequal Lto the' eiective area of the piston 94.I v This Vpressure in they mainV valve cavity 46 is resisted by compression of the heavy spring 186, whichgwhen compressed suiiciently will permit the pistons572 and 94 to move insuch directionas .to permit the 'pressureV inthe jack body 138 Vsecured by Ysuitablei bolts'or'cap screws/148 to the valverbody. 36. The va1vetbody'f138 is formed Vwith a central boreV 141iittedwith a'valve V,cylinder sleeve :142 having'an external'circumVferentialV groove 144,7and ports 146 which communicate cylinder V1,48Uin the sleeve., 'f 142;,With a passage `1570Y in 'the yalve b,ody138,whichY f communicates directly Vwith the passage V134. VThe cen- Vtral bore V141A communicates rwith the passage 130 `through an angular passage 152 formed inlthe valve body 138.Y

piston'type valvemernber 1541s Vslidable. in the Vvalve Vcylinder 148 and has a head exposed Vto thiefluid presi`Y Y VVsure in the main valve cavity 1.46 through .a passageway 156"formed in the valve 'body 36. Thepis'ton valve member 154 has an axial bore 157 and communicating lateral ports 158 and 16) by which the axialbore 157 communicates respectively with the passageways 150 and 152. Thus when the piston valve member 154 is in the position shown in Fig. 2, communication between the jack cylinder 12 and the space Within the cylinder 74 is established through the following path: passageways 134 and 159, ports 146 and 158, axial bore 157, port 160, and passageways 152 and 130.

The central bore 141 and the valve cylinder 148 communicate with a spring chamber 162 in the valve body 138 through a port 164 formed with a valve seat 166, the port normally being closed by a valve cap 168 screwed into the end of the piston valve member 154 opposite its head. The etective area of the seat 166 is precisely equal to the area of rthe head of the piston valve member 154.

The valve cap 168 is formed with a stem 17) projecting through the port 164 and having a washer 172 at its outer end adapted to bear against a spring 174, the compression of which may be adjusted by a relatively large diameter screw 176 threaded into the tapped outer end 178 of the spring chamber 162. A lock nut 18) maintains the screw in its adjusted position which should be that at which the force of the spring 174 is less than the hydraulic pressure on the head of the piston valve member 154 obtained during lowering of the elevator,

as determined by the adjustment of the screw 124. The

spring chamber 162 is vented to the atmosphere through a drain port 182.

When the system is idle with the elevator at its lower position having come there after a descent, the valves 24 and 19 will be closed and the uid in the system will only be that necessary to sustain the weight of the elevator and the load carried during the last descent. With the hydraulic pressure produced by the weight of the empty cage 18 alone present in the cavity 46, fthe piston 72 will have been moved to its extreme outward position, contacting the inner face of the cap 78, since the spring 1136 will have been adjusted by the screw 124 so that its force will be just less than enough to prevent such full travel of the piston 72. Y

When the hydraulic pump 32 is run to raise the elevator, the hydraulic pressure in the line 36, 22 and in the valve chamber 46 rises to open the valve member 52, and as the total areas of the slots 69 in the valve member 52 will normally be inadequate to pass the full ow of liquid in the reverse or toward the jack 14 direction without a substantial pressure drop, the valve 52 will open fully, leaving only the guide wings 62 within the opening 59, compressing the spring 9) and with the valve movement limited by contact of the cup 84 against the bottom of the axial bore 82. When the pump is stopped and its check valve closes, the uid ow from the pump 32 to the jacl: cylinder 12 will stop and the spring 90 will return the valve 52 to its fully closed position.

When the elevator is to be lowered, the jack cylinder 12 is vented to the reservoir 28 through the control valve 10, conduit 22, lowering valve 24 and conduit 26. The rate or" descending speed is determined by the setting of the lowering valve 24. In those elevator installations not incorporating the control valve 10, the actual speed of descent of the elevator depends upon the load imposed on the elevator, heavier loads producing faster speeds through an increase in the volumetric rate of fluid tiow from the jack cylinder 12 to the reservoir 28. The control valve 19, however, automatically regulates this iluid ow from the jack cylinder 12 to the reservoir in accordance with the setting of the lowering valve 24.

When the lowering valve 24 is opened fluid under pressure ows from the valve chamber 46 to the reservoir 28, and, a fall in pressure in the cavity 46 results. Since the uid pressure in the jack cylinder 12 has no effect on the valve position under normal conditions, the spring 106 moves the piston 72 and valve member-52r inthe valve opening direction to permit hydraulic fluid to flow from the jack cylinder 12. As the uid is throttled by the restriction through the -partially uncovered slots 60 there vis a drop in its pressure, and fthe spring 106 will move the valve member 52 in the opening direction until the pressure in the chamber 46 equals the pressure exerted by the spring at its adjusted setting. The proper setting is that obtained when an empty car 18 is descending at the maximum speed setting of the lowering valve 24, and the control valve components are shown in this position in Fig. 2.

Thus, the valve 52 when properly set automatically throttles the normal ow of hydraulic tluid through the port or opening 50 to produce a substantially fixed pressure in the valve chamber 46 during lowering of the elevator cage 18. Since this ixed pressure is transmitted through the conduit 22 to the lowering valve 24, that rate of ow of liquid determined by the setting of the valve 24 is always produced, and, consequently, the rate of descent is maintained substantially uniform or constant and determined solely by the setting of the valve 24.

It has been noted previously that the eiective areas of the piston 72 and the piston 94 acted on by fluid under pressure in the cylinder 74 diier by the etective area of the valve member 52 which is exposed to the same pressure, namely the jack cylinder pressure, and that pressure has no nuence on the position of the pistons 72 and 94. And whenever during lowering ofthe cage 18, the pressure in the valve chamber 46 exceeds that corresponding to the setting of the spring 106, the piston 72 and valve member 52 move in the valve closingrdirection to establish equilibrium between chamber pressure and spring compression and vice versa. It is, therefore, the throttling etect of the valve member 52 and the valve positioning by the spring 196 to produce a substantially constant or uniform pressure in the chamber 46 that produces the substantially constant uid flow and even descent of the elevator at any rate of speed for which the lowering valve 24 may beset.

When the elevator is to be stopped the lowering valve 24 will be operated to closed position and this operation is accomplished gradually. The reduced flow of iluid through the valve slits 66 and opening 50 into the valve chamber 46 will decrease the throttling pressure drop through the slits and the pressure will rise in the valve chamber 46, moving the piston 72 and valve member 52 against the force of the spring 106 in the valve closing direction. When the lowering valve 24 has reached its fully closed position, the valve member 52 will also be fully closed and the elevator will be halted because the iluid flow has stopped.

During the normal operation of the control valve 10 in maintaining the rate of iluid iow from the jack cylinder 12 constant and in accordance with the setting of the lowering valve 24, the pilot or safety valve 132 is held in the position shown in Fig. 2 by pressure in the chamberl 46 with the valve cap 168 closing the port or passageway 164. Should there be a loss of pressure in the system which arises from a bursting of the line 22 or some other cause which transmits this loss of pressure to the valve chamber 46, the spring 174 moves the piston valve member 154 upwardly lifting the valve cap 168 from its seat 166 to open the port 164. The cylinder 74 is vented to the atmosphere and drains through the passageways 136 and 152, port 164, spring chamber 162 and drain hole 182. This movement of the piston valve member 154 also cuts o communication between the jack cylinder 12 and the control valve cylinder 74 so that the drained duid will not be replaced. Since there is only atmospheric pressure in the cylinder 74 and the pressure acting onfthe valve member S2 exceeds the force of the spring 106, the valve 52 will be closed fully and promptly, bringing the elevator to a stop. This action will take place whether there is a normal or reverse ow of Huid through the valve '72,'and the cylinder '74.

passageway/15.6 isof course omittedvor plugged.l

The control valve 19 may also be used solely as 'av safety device. K lnV Vthisarrangement the spring do Vand spi khousing girare omitted, as are the piston 94 and cylinder 10 immediately preceding the fault causing the loss of pressure in the chamber 46 or `downstream of the Oritice 50. l Y

It should be noted that this same action is obtained if the loweringk speed is adjusted to a value in excess of the capacity of the valve *52' at the largest opening obtainable by inward motion of the piston 72, so that the `pressure from chamber 46 exerted on the piston 154 will be less than that exerted by the spring l'fl on thepistonvalve memberV i541.

"lh'econtrolV valve is restored to normal operation byV settingthe valve 24 to .the Vup or Yelevator raising position and operating the pump 32 to establish normal opelV ating pressure in the line 22 andchamber 46. This pressure created by thereverse tlow of hydraulic iluid moves the piston valve member i154, downwardly to reestablish communication between the jack cylinder l2 and the control valve cylinder 75tand to close the port 164. Hence, it is not necessary to malte any adjustments at the control valve itself in'order to restore the system to operation after a test by an elevator inspector or after correctingrthe cause of pressure failure in the system.

lt was noted previously that ther-pressure in the balance chamberor cylinder space 74 wasexactly equal to that in the jacl: cylinder Vl2 when the control valve is functioning properly. From vthis it would seerrrto appear that exact regulation is impossible, since at high jack pressures the valve 5?, must be nearly closed during lowering, cornpressing. the springY N6 to its maximum degree, thereby raising its force and requiringa highvpressure in the valve cavity Li6 toetect a balance. This rise in pressurerinV the Vvalve cavity if 'Y witha consequent rise inspeed of descent of the cage .i3-nfs overcome Vby leakage from the Vcylinder 7d past the VpistonV 72. to the cavity or vchamber 46'.` The'leakage is Vpossible because the piston 72 does not fluid tightly seal against the *wallY of cy1inder74, and

VAsum .et the effective areas of the valve seat Se and the balance cylinder 94. Vlfrthis is done the effect or the leakage must be avoided, either by packing the piston 72 against the'wall of the cylinder '/"iY or by making inlet passage to the cylinder 74 through the pilot valve generous inV size. Y' v A' n Y l The control valve it) may be modiiied slightlyV touse'it `solely as Va speed control device;V To (do this it is necessary to omit the pilot valve 132 and Yto'connejct the pasand the 'Y sarvewal i3d-duced' to the assagevva 3.359,'

96. The cap "i3 is made solid to become the head tort'ne cylinder 7.4' and'jack pressure is appliedrto theentire face Vof the pistonj?. in the'cylinder 74. The control valve elements are then normally biased to the position yshown in Fig. the position in whichan empty elevator cage l Y is loweredlat maximum speed setting of the lowering valve fat, kandwllenithere is a loss or"V pressure in the chamber 46 thepilot valve i232 will operate as Vpreviously.described to vent Ythe cylinder 74 and the rinievssureV on thefhead ofV Y This offers a means of checkingthe per-K formance of the safety featurezof the novel control valve by an elevator'inspector Vwithout V'actually"tneeching the This leakage would not result in mais@ 'of an elevator constant at the rate determined by the set- Y ting of the lowering valve, and Ywill bring the elevator to Va halt should there be a pressure failure in Vthe Vsystem communicable to the control valve it?. f

While preferred embodiments of the control valve constituting this invention'have been shown and described, it will be apparent that further modifications and Vvariations thereof may be made without departing from the underlying principles of the invention. It is, therefore, desired by the following claims to include within theV scope of the invention all such variations and modiiications by which substantially the results of this invention may be obtained through the use of the same or equivalent means.

What is claimed as new and desired to be secured by United States Letters Patent is: Y Y

l. A control valve for regulating the rate ot iiow of a lluid under pressure through an orifice comprising means forming a valve cavity downstream of andV communi-V cating withthe orilice and having an opening therefrom, a throttling valve member inV the orifice and movable therein to various positions from fully closed Vto fully open to control the rate of flow of uid into said cavity, valve mer. ber positioning means connected to said valve membernnd sensitive to Huid pressuredownstreamof the orifice and in said cavity'to adjust the throttling etect of said valve member, Vsaid valve member having offsetting areas acted upon by upstream fluid pressure sotthat the up-v streamuid pressure doesk not alect the position ofthe valve member thereby to maintain the downstream'uid pressure in said cavity substantiallyl constant, andrsecond means sensitive toA a fall in the downstream fluid pressure Ybelow a predetermined value to render inehiective said valve member positioning means, therebyto permit higher pressure upstream ofthe orice to close said valve member in the orifice to Vstop fluid ow therethrough.

' 2. A control valve for regulating the Vrate Vof flow of a fluid under pressure through an orifice comprising means forming a valve cavity downstream of and communicating with the orifice and having an opening therefrom, a'

to saidvalve member and sensitiveto iluid pressure downstream of the orilce'and in saidcavity to adjust the, throttling ctect of said valvefmember, thereby to maintain the Vdownstream `fluid pressure vin .saidV cavity substantially constant, said last named means including means to com-V pensate or Ythe eiect Vof Vupstream fluid pressure acting on said valve member. Y e

3. A control valve for'regulating the rate of ii'ow ofea iiuid under pressure throughjan orifice comprising means to adjust the throttling eect of-s'aidvalve member, thereby to maintainrthe downstream'iiuid pressuregin said cavity substantially constan t,said last namedrmeans comprising a pairrof interconnected opposed diierentialnarea L piston-cylinder means,y aV passageway connectingfsaid .piston-cylinder means` with alpoint of the oiiiice to receive iluidV under pressure therefrom; sothat the upstream uid pressure normally does not aectthe position of said valve member,` and biasingmeans biasing said Y valve member to open position.

arseao 4. A control valve for regulating the rate of flow of a uid under pressure through an orifice comprising means forming a valve cavity commrnicating with the orifice and having an opening therefrom, a throttling valve member in the orifice and movable to various positions to control the rate of ow of iiuid into said cavity, a iirst cylinder having one end communicating with said cavity, a piston slidable therein, a second cylinder communicating with the second end of said first cylinder, a piston slidable in said second cylinder and connected to said iirst cylinder piston so that said pistons move together, said pistons having a dilerence in areas equal to the effective area of said throttling valve member, a passageway connecting said cylinders between said pistons to receive uid under pressure from that side of the orice opposite said cavity, lost motion means connecting said valve member to said pistons, and loading means biasing said pistons and said valve member to open position, whereby the uid pressurey in said cavity is maintained substantially constant and at a value determined by said loading means.

5. A valve for controlling the ow of a fluid under pressure through an orifice comprising means forming a valve cavity downstream of and communicating with the orifice and having an opening therefrom, a valve member movable in the oriiice to control the ow of fluid into said cavity, valve member positioning means connected to said valve member, means communicating fluid under pressure from upstream of the orifice to said valve member positioning means to move said valve member toward open position, and means sensitive to a fall in fluid pressure downstream of the oriice'in said cavity below a predetermined value to interrupt the communication of fluid under pressure to said valve member positioning means thereby to permit higher pressure upstream of the oriiice to move said valve member to closed position.

6. A valve for controlling the ow of iiuid under pressure through an orifice, comprising means forming a valve cavity downstream of and communicating with the orice and having an outlet therefrom, a valve member movable in the` orifice to control the oW of fluid into said valve cavity, valve member positioning means connected to said valve member, said last named means including a cylinder and a piston reciprocable therein, said piston being connected to said valve member, a passageway connecting said cylinder on the head side of said piston with the fluid under pressure upstream of the orice whereby the uid under pressure in said cylinder acts on said piston to move said valve member to open position, a drain port, a valve controlling uid ow through said passageway and said drain port, means biasing said valve to passageway closing and drain port opening position, and means sensitive to uid pressure downstream of the orifice in said cavity and acting in opposition to said biasing means to Jhold said valve in passageway opening and drain port-closing position'as long as the downstream pressure remains above a predetermined value, whereby a fall .in downstream fluid pressure below said predetermined value permits said biasing means to close said passageway and open saiddrain port, said cylinder then emptying through said drain port and higher pressure upstream of the orifice moving said valve member to closed position.

7. In a hydraulic elevator control system having a jack-cylinder, a cage supporting plunger reciprocable therein, and a lowering valve adapted to receive hydraulic fluid under pressure from the jack cylinder to regulate therate of speed of elevator descent, a reverse ow control valve comprising in combination a control valve body adapted to be mounted on Vthe jack cylinder and having a"valve cavity therein, a constantly open port in said valve body adapted to be connected to the lowering valve, an opening in said valve body upstream of 'saidvalve cavity and adapted to communicate with the jack cylinder and through which hydraulic fluid ows in a irst direction into said valve cavity, a throttling' valve member slidable in said opening and movable to various positions therein to control the rate of uid flow in said rst direction into said cavity, said throttling valve member having an effective area exposed to fluid under pressure upstream of said valve opening tending to move said throttling valve toward closed position, means forming a rstcylinder having one end communicating with said valve cavity, a piston slidable theref in, means forming a second cylinder communicating freely with the second end of said rst cylinder, a piston slidable in said second cylinder and connected to said rst cylinder piston so that said pistons move together, said pistons having a diierence in areas equal to the eiective area of said throttling valve member, a passageway connecting said cylinders between said pistons with a point upstream of said valve opening, lost motion means connecting said valve member to said pistons and including means biasing said throttling valve member to closed position so that fluid may iiow under pressure in a second and reverse direction through said control valve, loading means biasing said pistons and said throttling valve member to open position, whereby the fluid pressure in and the fluid tiow through said valve cavity in said irst direction is maintained substantially constant, means forming a pilot valve cylinder having one end open to said valve cavity, a drain port, a valve plunger in said pilot valve cylinder and normally closing said drain port, means biasing said valve plunger to open said drain port, and said valve plunger lying across said passageway and having a passage therethrough which maintains said passageway open when said drain port is closed and closes said passageway when said drain port is open, said cylinders draining through said drain port when fluid pressure in said cavity falls below a predetermined value whereby iiuid under pressure upstream o said valve opening closessaid throttling valve member.

8. In a hydraulic elevator control system having a jack cylinder, a cage supporting plunger reciprocable therein, and a lowering valve adapted to receive hydraulic fluid under pressure from therjack cylinder to regulate the rate of speed of elevator descent, a control valve comprising in combination a control valve body adapted to be mounted on the jack cylinder and having a valve cavity therein, a constantly open port in said valve body adapted to be connected4 to the lowering valve, an opening in said valve body upstream of said valve cavity and' through which hydraulic fluid ows into said valve cavity, a throttling valve member slidable in said opening and movable to various positions therein to control the rate of iiuid flow into said cavity, said throttling valve member having an eiective area exposed to uid under pressure upstream of said valve opening tending to move said throttling valve toward closed position, means forming a rst cylinder having one end communicating with said vali e cavity, a piston slidable therein, means forming a second cylinder communicating freely with the second end of said rst cylinder, a piston slidableV in said second cylinder and connected to said rst cylinder piston so that said pistons move together, said pistons having a difference in areas equal to the eiiective area of said throttling valve member, a passageway connecting said cylinders between said pistons with a point upsteram of said valve opening, means connecting said valve member' to said pistons, loading means biasing said pistons and said throttling valve member to open position, whereby the fluid pressure in and the fluid flow through said valve cavity is maintained substantially constant.

9. In a hydraulic elevator control system havingY a jack cylinder, a cage supporting plunger reciprocable therein, and a lowering valve adapted to receive hydraulic iiuid under pressure from the jack cylinder to regulate thehrate of speed of elevator descent, a control valve Y Y 1 1 Y i i comprising a control valve body adapted to be mounted on the jack cylinder and having a valve cavity therein, a constantly open port in said valve body adapted to be Vconnected to the lowering valve,an opening inY said valve body upstreamof said Vvalve Vcavity and through which hydraulic fluid flows into said valve cavity, a

'valve member slidable in said opening and controlling the flow of iiuid Vinto said cavity, said valve member having an effective area exposed to fluidunder pressure upstream of said valve opening tending to move said valve member toward closed position, means forming va. cylinder having one end communicating with saidl valve cavity, arpiston slidable therein, said piston having anV area greater than the effective area of said valve member, a passageway connecting saidcylincler at the Y head of said piston with a point upstream Vof the valve cylinder draining through said drain port when fluidV pressure in said cavity falls below a predetermined value whereby huid under pressure upstream of said valve opening closes said valve member. l

l0. A control'valve for regulating the Yrate of flow of fluid under pressure through an orifice, comprising means forming a valve cavity downstream of and communicatingrwith the orifice and having an opening therefrom, a throttling valve member in the orice and movable to n various positions thereinvto control the rate of flow of iiuid through the orifice and into said cavity, and valve member positioning means connected to said valve member and sensitive to fluid pressure downstream of the orifice and in said cavityto adjust the throttling and pressure dropxeffect of said valve member, thereby to maintain the fluid pressure inrsaid cavity substantially y constant, said last named means Vcomprising a pair of Y interconnected opposed differential area piston-cylinder' meanslacted upon by downstream pressure uid in said cavity, a passageway havingY a fluid owrrestriction Vtherein' connecting said piston-cylinder means with a point upstream of the orifice to receive fluid under pressure therefrom to' cause said piston-cylinder means to tend to move said valve member in valve opening direction, and

compressible springmeans biasing said valve 'member to'openV position, whereby excessive pressure upstreamk of the ori'ce tending-to cause said piston-cylinder means to e open said valve member to increase pressure-in said cavity is loffset byY leakage from said piston-,cylinder means intoV said valve cavity and a pressure-drop across said restrici tionV substantially equal tothe gain in force exerted by said spring means due toY compression thereof as said valve member is movedV to a highlyrthrottlin'g position.

ILA' controlvalverfor regulating the rate of How of uid'under pressure through an oriiice, comprising means forming ja valvecavity Vdownstream ofnthe'orice and Y communicating with the orice andrhavngan opening therer"roma throttling Yvalve member inthe oriiice and Vvalve, member and sensitive to downstream fluid pressure in saidrcavity'to adjust Ythe throttling and pressure drop ":movabie therein to' various positions Vto control the rate ofgtlow of iluid through said orice 4and into v'said cavity,

ide-,66o

cylinder means acted upon by downstream pressure fluid in said cavity, a passageway connecting said piston-cylinder means with a point upstream ofthe orifice to receive iluid under Vpressure therefrom to cause said piston-cylinderrmeans to tend to move said valvermember in valve opening direction, compressible springrmeans biasing said Y valve member to open position, and'saidvvalve member positioning means including means tocompensate for excessively high pressure upstream ofthe orifice tending 5 to cause opening of said valve member suicie'ntly to reduce the throttling eiect VVof said valve member Vand permitrise of pressure downstream of the orifice vabove said predeterminedvalue.V Y Y l2. AV control valve foi-'regulating the rate of ilow offlluidunder pressure through an orifice, comprising means formingra valve cavity downstream offan'dcornmunicating with the orirce and having an opening therefrom, Va throttling valve member inthe orifice and movable to various positions therein to control the .rate of oiv of fluid into said cavity, said valve member having an effective area exposed'to fluid under pressure upstream o'f the orice tending to close said valve member, a rst cylinder having one end communicating with said cavity, a piston slidable therein, a second cylinder com-V municating with `the second end of said iirst cylinder, a piston slidable in said` second cylindertand connected to said iirst cylinder piston so that said pistons move together, said pistons having a diierence in area equal to the eective area of said throttlingpvalve member, means connecting said valve member to said pistons, av passageway having a fluid low restriction thereinconnesting said cylinders between said pistons to receive iluid under pressure from a point upstream of the oriceV to cause said interconnected pistons to tend to move said valve member in valveopening direction, and comprest sible spring means biasing said valve member to open position, whereby excessive pressure upstream ofthe orifice tendingV to cause said pistons to open said valveY member and increase the pressure downstream of the orice is oisetV by leakage from said iirst cylinder intoY said valve cavity and a pressure drop across said restriction substantially equal to the gain Yin forceexeirtedY by Y said spring means due to compressionthereof as said valve member is moved to a highly ,throttling position.

13'. AV control valvetor regulating'the V,ratevof ow of iiuid under pressure throughY an'orice, comprising i: means forming al valve cavity'downstream of and com'- vmunicating with the oriice and having an opening therefrom, a throttling valve member in the orifice and movable to various positions therein to control thezrate of flow of fluid into said cavity, said valve member 4having anciective areaY exposed to Yiiuid under pressure upstream of the oricelt'ending to close said valve member,VVV

y,a rst cy Ender having one end communicating withsaid cavity, a piston Vslidable'rtherein, a -secondfancl'smaller ,i ,diameter cylindercommunicating with the second 'end v of said rst cylinder, a piston slidable in said second diterence in areas slightly greater thanthe effective area'.

i of said throttling V,valve member, means {connecting said*- VvalveY member to said-pistons', a passageway connectingV f1,

said cylinders betweenY said pistons Vto receive fuid under'- Vpressure Afrom Ta point upstrear'n'of'theY Yoriticefto cliurSe said interconnected 'pistons to tendl to move said valve andV vaive member positioning means connectedtosaid L etect Vof said valve member, thereby to fmaintainthe l duid pressure in said cavity ksubstantially constant Vata 'Y predetermined valve, said last named means comprising 'member inzrvalve Vopening Ydirection, and i compressible spring meanrsrbiasing said valve member to open position,

wherebyrthe duid-'pressure Vin Vsaid cavity ismaintained substantially constant and at a value determinedbyrs'aid Y biasing spring even though `the pressure upstreamQofftle'V Vo'rice oppositeV said cavity shallbecome excessively high. Y

(References Voniiolloiviilg page).V`

References Cited in the le of this patent UNHED STATES PATENTS Cornelius May 19, 1857 Herdman Oct. 31, 1899 Matthews Jan. 9, 1917 Jones May 13, 1919 14 Greenlee Apr. 17, 1934 Wassall Apr. 1, 1947 Ives Mar. 14, 1950 MacGlashan, Jr. Dec. 1, 1953 FOREIGN PATENTS France Jan. 31, 1951 

